However, Citi analyst Itay Michaeli says it's not that simple. "It is true that an aging vehicle fleet gives rise to a significant replacement opportunity (more scrap), but only if sales stop falling short of scrap, which is a function of future U.S. vehicle density (vehicles-per-household)."

"Understanding the direction of vehicle density is perhaps the single most important (and often overlooked) factor of automotive investing."

Michaeli surveyed 2,200 people and found that indicators for the future direction of vehicles-per-household have showed "surprising resilience" since he last conducted the survey in May.

"Overall, the survey predicted a 2.2% decline in vehicle density in 2-years," said Michaeli. A 1% decline in the density ratio generates at least 1 million units of demand. His current forecasts for light vehicle sales are 12.8 million in 2011, 13.9 million in 2012, and 14.5 million in 2013.

Michaeli thinks macroeconomic worries are causing auto sector stocks to be priced for less than 12 million units in 2012. But he thinks this may be an opportunity.

"The gap between perception and our analysis is what we seek to exploit, because unlike positive micro data points that have been a ignored, a resilient U.S. [auto sales rate] could restore sentiment."